Downhole pumps are widely used in oil and water wells. It is highly desirable to remove sand and other solid particles from the well fluids before they enter the downhole pump to reduce wear and plugging of the pump and other components. Repairing or replacing downhole pumps is expensive as a result of rig time, labor costs, part costs, lost production and the like.
When large quantities of sand flow into the well bore, it is desirable to stop or reduce the sand flow. Various sand control systems have been utilized heretofore to stop or reduce the sand flow into the well bore. However, even with sand control systems, in many instances sand or other solid particles are entrained with the liquid pumped through the downhole pump. Screens or filter openings have been utilized heretofore in the casing or other members to restrict the flow of solid particles. However, if the filter openings are too small, the openings will eventually become plugged, and if the filter openings are too large, solid particles will flow through the openings. In may wells, the quantity of sand flowing from the formation is relatively small but sufficient to wear or plug the downhole pump. The sand flow is often relatively large each time the pump is started, but is reduced or ceases after a time period of continuous flow. For example, gravel packs are widely used to keep sand from flowing into the well bore. While gravel packs may be utilized in a satisfactory manner to restrict the flow of sand in some formations, they are not effective in other types of formations. In such formations, the wells have to be pumped at a low rate to reduce the amount of flowing sand and if production rate is not sufficient to justify the high maintenance cost then such a well is usually abandoned.
U.S. Pat. No. 4,900,453 dated Feb. 13, 1990 shows an oil separator in which a spiral guide is provided for downward fluid flow to separate solid particles from liquids. However, the spiral guide does not show a downward helical path for the fluid which decreases in cross sectional area between upper and lower ends of the spiral path to provide a relatively smooth flow at a progressively increasing velocity.